This invention pertains to an automated top head and stem guide assembly for vertical vessels such as coking drums. It pertains particularly to an automated removable top head cover unit used in combination with a removable stem guide unit, and to a method for remote removal and replacement operation for these units attached onto the vessel top head flanged opening.
During operation of delayed coking drums for the coking of various heavy hydrocarbon materials in petroleum refinery operations, the resulting coke is deposited progressively on the inner walls of the drum and when full must be periodically removed, usually at 36-48 hour intervals. A typical decoking apparatus for such coking drums is disclosed by U.S. Pat. No. 4,611,613 to Kaplan. Such coke removal from coking drums is accomplished through an opening in the lower end of the vertically-oriented drum, after the coke is cut away hydraulically by a device inserted through an opening in the coking drum top head. Removal of the large top head cover to permit inserting the cutting device is usually accomplished manually by using hoisting equipment. However, because the coking drum operates at relatively high temperatures of 500-900 degrees F., such removal of the hot coking drum top cover by manual means is slow and somewhat hazardous, and is therefore undesirable.
Various mechanical unheading devices for large containers have been disclosed in the prior art. For example, U.S. Pat. No. 3,751,854 to Huwyler et al discloses a lifting and swing mechanism for a crucible type furnace. Also, U.S. Pat. No. 3,944,472 to Lowe discloses a pivotable device for removing top lids of coke ovens. However, these prior art devices have been found to have serious deficiencies when applied to unheading the top heads of coking drums. Such deficiences have now been advantageously overcome by the present invention.